Field of the Invention
The invention relates to a laser machining head, in which beam-shaping optics, in particular focusing optics, collimator optics or zoom optics, are displaceably or adjustably held.
Brief Description of the Related Art
During the machining of a workpiece by means of a laser machining head, in particular during laser cutting or welding, a laser machining head is usually provided with a housing in which focusing optics, collimator optics, zoom optics or are arranged. A laser beam running through the laser machining head to a cutting nozzle is focused by focusing optics such that a workpiece can be machined. The optics for shaping the laser beam are held in the laser machining head in this context such that the optics are adjustable relative to the housing of the laser machining head. Here, the optics can be adjusted firstly in a plane perpendicular to the laser beam and secondly in the longitudinal direction of the laser beam.
DE 295 07 189 U1 discloses a connecting head for machining a workpiece by means of a laser beam, in which the focusing optics for the laser beam are held displaceably on a slide-in unit, which can be inserted into the housing of the connecting head. In order to displace the optics in the direction of the longitudinal axis thereof, a manual drive which operates like a spindle drive is provided here.
DE 196 22 413 discloses a cable drive as adjusting drive for positioning optics in a laser machining head. In this case, it is disadvantageous that, even with a cable diameter of only about 1 mm and bending radii of about 20 mm within the cable, abrasion is produced by friction between the individual wires. As a result, the interior of a machining head and in particular the optics therein can be contaminated.
In order to circumvent the problem of contamination of the optics in known laser machining heads, which is caused by abrasion and/or lubricants if displacement of the optics is carried out in accordance with the spindle principle or by means of a cable drive, it is already known to provide a displacement device for the optics which has a linear motor with contact-free drive.
A displacement or drive device having such a linear motor with contact-free drive (direct drive) is known from German utility model DE 20 2009 012 924 U1.
The disadvantage here is that the optics can be moved in an undesired manner and thus the focal position can be shifted if high accelerations act on the direct drive from outside, since then inertial forces can occur, which can be greater than the magnetic holding force. If this effect is to be avoided, a brake or a direct drive having greater dimensioning can be incorporated. This procedure contradicts a small overall size and the lowest possible costs.
DE 43 17 384 A1 discloses a laser machining head, the beam-shaping optics of which are displaceable in the longitudinal direction of the laser beam by a worm drive. However, as is known, this type of drive is sluggish and relatively inaccurate on account of the spontaneous play of the worm drive.
U.S. Pat. No. 5,546,238 A relates to zoom optics with a high-speed lens drive and, in order to displace the optics, shows a belt drive having a circulating belt which is led over two rolls. For displacement, the individual lens groups of the optics can be coupled as desired to the circulating belt via piezoelectric clamps. Here, the belt is led over the driving rolls without friction.
DE 196 28 857 A1 relates to a connecting head for machining a workpiece by means of a laser beam, the beam-shaping optics of which are arranged in a cartridge which can be inserted into a carrier unit in the laser machining head. In order to displace the carrier unit in the direction of the optical axis, an electrically driven geared motor is provided, the motor shaft of which extends parallel to the optical axis. Seated on the motor shaft is a drive gear for a toothed belt, which is laid around a further drive wheel which is seated firmly on a spindle in order to rotate the latter when the motor rotates. In order to displace the carrier unit, the spindle interacts with a spindle nut, which is fixedly attached to the side of the carrier unit.